It has come to be recognized that substantial economies can be achieved in the repair and reconstruction of asphalt pavements if crushed salvaged asphalt material, reclaimed from a previously laid pavement, is mixed with virgin (unused) aggregate. The mixing of asphalt materials and the introduction of salvaged asphalt materials generate a considerable amount of particulates which are carried along in the gases which are being exhausted to atmosphere. Environmental requirements demand that these exhaust gases be treated so as to remove the major amount of particulates from the gases before they are exhausted.
One approach to this problem is disclosed in U.S. Pat. No. 3,693,945 wherein a spray mechanism is provided to spray hot bituminous liquid onto the aggregate passing through the cylinder mixer. This bituminous spray was intended to also coat the particles moving with the exhaust gases and thence would fall out of the exhaust gases. In another version there is suggested that the dust ladened gases are back flushed through the mixer and into a centrifuge separator where the heavier dust particles are retained. The gases and entrained lighter dust are then directed into an air washer and hot bituminous liquid utilized to coat the dust. As is apparent, this apparatus was very expensive, requiring additional equipment for dust removal.
In U.S. Pat. No. 3,840,215, another system is disclosed for handling the dust problem in asphalt mixing plants. As shown, dust knock-out boxes are provided which are distinct and separate from the mixing apparatus itself. Ducts from the mixing apparatus are connected to the knock-out boxes directing the dust laden gases from the mixing apparatus into the boxes. Within the knock-out boxes a baffle is provided to provide a circuitous gas flow path through the boxes. These baffles are supposed to interrupt the air flow causing the dust and solid particles to drop out of the gases and into a collecting drawer.
In U.S. Pat. No. 4,034,968, there is disclosed apparatus in the form of an accumulator collar to prevent the venting of hydrocarbons into the atmosphere. The collar is hollow and extends around the upper mixing drum exterior covering outlet ports through which the mixed asphalt exits from the drum. A pipe which communicates between the collar and the furnace and creates a draft through the pipe to assist in pulling gases from the collar into the furnace chamber. Thus, the gases are recirculated in a manner similar to the internal combustion engine of the present day automobile.
By contrast with respect to the prior art, the general object of the present invention is to provide a scrubber apparatus operable to treat particulate laden gases from an asphalt drum mixer (or aggregate dryer) to remove the dust therefrom prior to the gases being exhausted to atmosphere.
Another object of the present invention is to provide a gas scrubber for cleaning the exhaust gases from an asphalt drum mixing apparatus, or aggregate dryer.
Still another object of the present invention is to provide a gas scrubber for cleaning particulate from the exhaust gases of an asphalt drum mixing apparatus or aggregate dryer which has no moving parts.
Yet another object of the present invention is to provide a wet gas scrubber for cleaning the particulates from the exhaust gases of an asphalt drum mixing apparatus, or aggregate dryer.
A further object of the present invention is to provide a gas scrubber having a ring dam to prevent particulate laden water from entering the exhaust gas stream from a surface of the scrubber system.